Last month, Facebook introduced "paid messages," a feature where users pay a $1 fee to have their private message sent to an individual's "strict filtering inbox" instead of an obscure "other" inbox. Before the change, Facebook users were allowed to send a private message free to someone they didn't know or weren't connected with.

"Several commentators and researchers have noted that imposing a financial cost on the sender may be the most effective way to discourage unwanted messages and facilitate delivery of messages that are relevant and useful," Facebook said in a Dec. 20 statement.

Facebook told ABCNews.com that the $100 private message offer is an experiment not just with Zuckerberg but to those with a significant number of subscribers. Remember, subscribers are people who aren't your friends but can view the content you share with them because they follow you. Facebook calls these subscribers a broader group of friends.

"This test will give a small number of people the option to pay to have a message routed to the 'inbox' rather than the 'other' folder of a recipient that they are not connected with," said Facebook. "If you select strict filtering, you'll see mostly messages from friends in your inbox."

Since reaching 1 billion users last October, the social network giant has been revamping its privacy settings and changing the look and feel of the Facebook experience online and in mobile devices.

Facebook is "testing extreme price points to eliminate spam" with its new messaging fee, the site said. As users become more acquainted with the new messaging fee, they'll notice the number of messages received will be limited to a maximum of one a week.

Facebook told ABCNews.com there's a lot of filtering happening resulting in getting the messages that are only meant for you, the user. As far as the reaction to Facebook's new "paid messages" feature, Facebook offered no comment.